Prefabricated water-proofing bitumen-mix membranes are known, used for water-proofing external surfaces of buildings such as roofs, terraces in apartment blocks, industrial warehouses, private residences, but not only.
Plants for making bitumen-mix membranes are also known. They normally comprise an application unit configured to apply on a support, also called brace, a bituminous material or mixture, such as oxidized bitumen, distilled bitumen or modified bitumen.
Such plants also comprise at least an apparatus to make a protective and enhancing finishing cover on at least one surface of the prefabricated bitumen-mix membrane. The cover is usually made with solid particles with a mineral base, such as slate, basalt, ferrite or suchlike in the form of flakes, granules, sand or grit, hereafter indicated generically by the term grains.
The solid particles also have the function of protecting at least the surface of the bitumen-mix membrane exposed to atmospheric events, for example rain, snow, ice or solar radiation.
Apparatuses are also known that, by depositing the solid particles, obtain enhancing decorations on the water-proofing bitumen-mix membrane.
These apparatuses usually comprise a distribution device that includes at least a hopper for containing the solid particles and a transfer member configured to transfer the solid particles in a metered manner from the hopper to the membrane to be covered.
The transfer member, for example a rotary drum or a belt wound between two cylinders and selectively translatable between the two cylinders, is provided on an external surface with a plurality of cavities, each of which having a size and shape substantially similar to those of the decoration to be reproduced on the surface of the membrane to be covered.
The cavities are filled on each occasion with the solid particles in the hopper.
The activation of the transfer member determines the transfer and release onto the prefabricated water-proofing bitumen-mix membrane of the solid particles to obtain the desired decorations on the membrane.
Given the particular configuration of the cavities, which substantially reproduce the same shape and size of the decoration to be obtained, these apparatuses do not allow to release the solid particles onto the membrane in a desired and controlled manner. In fact, during the rotation of the transfer member, the particles are not suitably held by the cavities and are unloaded together, as soon as the cavity is disposed in a vertical or sub-vertical position.
This entails both a blurring of the decoration with respect to the ideal contour consisting of the template, and also a deposit of a non-uniform layer of solid particles on the surface of the bituminous membrane, which can lead to a dis-homogeneous esthetic effect, and at some points reduces the efficacy of the covering given by the solid particles against atmospheric events.
A transfer member is also known from documents U.S. Pat. No. 5,814,369 and US-A-2002/0160108, provided with a support surface on which a plurality of cavities are made. Each cavity is suitable to receive the solid particles that are delivered by feed devices.
The transfer member can be a rotary drum, as in the case described in U.S. Pat. No. 5,814,369, or a conveyor belt wound between two cylinders as described in US-A-2002/0160108.
To prevent an uncontrolled delivery of the solid particles contained in the cavities, U.S. Pat. No. 5,814,369 describes a holding device located in contact with part of the support surface of the rotary drum and which, for at least the part of the support surface of the transfer member located vertical or sub-vertical during use, maintains the solid particles in the cavities of the transfer member.
The holding device comprises a flexible belt wound around a plurality of return rolls that define at least a segment of the flexible belt that positions itself adherent to the external surface of the rotary drum.
The presence of a flexible belt in contact with the support surface is not able to ensure that only the solid particles contained in the cavities are transferred to the surface of the bituminous membrane. In this solution, in fact, possible solid particles that are interposed between the conveyor belt and the support surface of the transfer member and which are not contained in the cavities are also transferred to the membrane to be enhanced. This results in decorations that are not very precise or defined.
The solid particles that are interposed between the flexible belt and the support surface increase the wear to which the transfer member is subjected during use, due to the abrasive action of the solid particles. This reduces the working life of the transfer member and/or the flexible belt, and requires frequent maintenance operations and replacements of the components.
One purpose of the present invention is to obtain an apparatus to make decorations on prefabricated water-proofing bitumen-mix membranes that allows a better precision in defining decorations and that at the same time allows to obtain a greater uniformity of the covering layer obtained using solid particles.
Another purpose of the present invention is to make an apparatus to make decorations that is simple and economical.
Another purpose of the present invention is to obtain an apparatus to make decorations that increases the working life of its components and reduces the maintenance operations on them.
Another purpose of the present invention is to obtain a plant for the production of prefabricated water-proofing bitumen-mix membranes with a pleasant appearance and provided with precious decorations that precisely fill the cavities and define the contours.
Another purpose of the present invention is to obtain an apparatus to make decorations on prefabricated water-proofing bitumen-mix membranes that is simple, economical and reliable.
The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.